AIDS Clinical Trial Group (ACTG) study to assess the safety of combination stavudine (d4T) and didanosine (ddI) therapy, to compare it to the safety of giving ddI alone, and to assess long-term and short- term changes in viral burden. Study objectives additionally include, estimation of disease progression and survival rates, and long-term and short-term changes in CD4 lymphocyte counts. In the laboratory, d4T has been shown to have activity against the HIV virus and, in some laboratory studies, was found to be less toxic than AZT to those cell lines in the body responsible for producing red and white blood cells. Ongoing research suggests that combination therapy with two or more antiretroviral agents, may be more beneficial than single-agent therapy in the long-term management of HIV infection.